What Is Cystic Fibrosis?
Cystic fibrosis (CF) is an inherited disease that causes
the body to produce mucus that's extremely thick and
sticky. The mucus in people with CF is thicker than
normal because CF affects cells in the epithelium
(pronounced: eh-puh-thee-lee-um), the layer of cells
that lines the passages in the body's organs. In a
person who does not have CF, the epithelial cells
produce a thin, watery mucus that acts like a lubricant and helps protect the body's tissues. In a
person with CF, however, the thicker mucus doesn't move as easily. This thick, sticky mucus clogs
passages in many of the body's organs and infection sets in.
The two organs that are most affected are the lungs and pancreas, where the thick mucus causes
breathing and digestive problems. The thicker mucus has trouble moving out of the lungs, so bacteria
can remain and cause infections. The thick mucus can also be found in the pancreas — an organ that
produces proteins called enzymes that flow into the intestine to support the body's digestion process.
Because the mucus can block the path between the pancreas and the intestines, people with CF have
trouble digesting food and getting the vitamins and nutrients they need from it.
CF can also affect the liver, the sweat glands, and the reproductive organs.
What Causes CF?
Approximately 30,000 people in the United States have been diagnosed with CF, which affects both
males and females. It's not contagious, so you can't catch CF from another person.
Cystic fibrosis is an inherited disease caused by mutations (changes) in a gene on chromosome 7, one
of the 23 pairs of chromosomes that children inherit from their parents. Cystic fibrosis occurs because
of mutations in the gene that makes a protein called CFTR (cystic fibrosis transmembrane regulator).
A person with CF produces abnormal CFTR protein — or no CFTR protein at all, which causes the body
to make thick, sticky mucus instead of the thin, watery kind. Cystic fibrosis results in blockage of
pancreatic ducts and air passages due to the inability to transport chloride (and sodium) out of the cell.
The end result is that water does not leave the cell and enter the extracellular fluid (ECF), resulting in
accumulation of thick, viscous mucus that clogs air passages and gland ducts.
People who are born with CF have two
copies of the CF gene. In almost all
people born with CF, one gene is
received from each parent. This means
that the parents of kids with CF are
usually both CF carriers — that is, they
have one normal and one defective
gene — but the parents may not have
CF themselves because their normal gene is able to "take over" and make the necessary CFTR protein.
Each child born to parents who are both CF carriers has a 1 in 4 chance of having the disease. Cystic
fibrosis occurs most frequently in Caucasians of northern European descent, in whom the CF gene is
most common — although people of other heritages can get the disease, too.
People who have a close relative with CF are also more likely to carry the
CF gene — approximately 12 million Americans, or 1 in every 20 people
living in this country, is a CF carrier. And most of them don't know it.
Parents can be tested to see if they carry the CF gene, but because there
are hundreds of specific CF gene mutations (not all of which are known),
genetic testing for CF won't detect everyone who is carrying a CF gene.
Doctors can also perform tests during pregnancy so prospective parents
can find out more about the chances that their child will have CF. However,
these tests also won't always detect a CF gene.
What Happens When You Have CF?
Symptoms include:
frequent lung infections or pneumonia
persistent wheezing
persistent cough with thick mucus
bulky, light-colored, foul-smelling bowel movements or diarrhea (because food isn't being digested properly)
failure to gain weight, even though the child eats normal amounts
very salty sweat
poor height growth
nasal polyps (small growths of tissue inside the nose)
frequent sinus infections
fatigue
In CF, the airway mucus is too thick and sticky. It traps particles like healthy
mucus but the cilia cannot move the mucus to the throat. The mucus clogs the
airways interfering with gas exchange by blocking air and makes it hard to remove
particles and germs from airways. People with CF get frequent lung infections that
can damage their lungs over time and require strong antibiotics along with stays in
the hospital.
They may have trouble growing or
gaining weight because of digestive
problems. Glands in the pancreas
make thick secretions that block
digestive enzymes from reaching
the small intestine.
The sweat glands in someone with CF release two to five times more salt, causing the classic CF sign
noticed by family when they kiss the child’s skin and notice the salty taste. The loss of too much salt
can cause problems and will be felt as tiredness, weakness, muscle cramps, and dehydration. Adults
with CF may also develop other illnesses, such as diabetes (a disease in which a person's blood sugar
is too high) or osteoporosis (a weakening of the bones). The ends of the toes and fingers may become
rounded and enlarged, a condition that's called clubbing.
Right now, there is no cure for CF. Even if symptoms are mild at first, they get steadily worse over
time.But there is hope. Fifteen years ago, most children with CF would die before reaching their teens.
Now, with new treatments available, more than half live into their thirties, and new research is leading
to the possibility of a cure. Statistics now show that nearly 40% of the people living with CF in the
United States are 18 years or older.
What Do Doctors Do?
If doctors suspect that a person has CF, they will order a
sweat test. In this test, the doctor or technician uses a
chemical and a very mild electrical current to cause sweating
on an area of skin, usually on a person's forearm (this test
doesn't hurt). The doctor or technician collects a large
amount of sweat in a pad and then analyzes it. If the test
results show a high level of chloride (a chemical in salt),
there's a possibility the person has CF. In some states in the
United States, all newborns are checked for CF with a blood
test, although the blood test isn't as good at detecting the
disease as the sweat test.
Doctors and people with CF can do several things to slow the progression of the disease and fight its
complications. To loosen mucus, people with CF exercise regularly and may use inhalers (like kids with
asthma use) or nebulizers that help deliver medication to the lungs.
Coughing helps people with CF clear the mucus from their lungs. They
may also take antibiotics to prevent or fight lung infections. Chest physical
therapy may also be an important part of a person's CF treatment routine.
After lying down in a position that helps drain mucus from the lungs, the
person has a helper, such as a parent, gently bang on his or her chest or
back to loosen the mucus. And a newer device called a therapy vest that
shakes the chest allows teens to be more independent by doing their
therapy on their own.
For digestive problems, a person with CF can take enzymes
by mouth in order to help digest food and get nutrients
from it. A doctor may also prescribe vitamin supplements
and a high-calorie diet.
Cystic Fibrosis
Questions:
1. What happens to people with Cystic Fibrosis?
2. What do scientists currently believe is the cause of CF?
3. Use the diagram below to explain how a membrane protein leads to thick sticky mucous in CF
4. Why does Alvin (the baby) have salt crystals forming on his skin? Explain how this happens.
5. What is the accepted treatment for children with cystic fibrosis?